Re: [f2fs-dev] [PATCH] f2fs: prevent meta updates while checkpoint is in progress

From: Sahitya Tummala
Date: Tue Apr 14 2020 - 05:59:28 EST

On Mon, Apr 13, 2020 at 10:42:37AM -0700, Jaegeuk Kim wrote:
> On 04/03, Jaegeuk Kim wrote:
> > On 04/03, Jaegeuk Kim wrote:
> > > On 04/01, Sahitya Tummala wrote:
> > > > Hi Jaegeuk,
> > > >
> > > > Got it.
> > > > The diff below looks good to me.
> > > > Would you like me to test it and put a patch for this?
> > >
> > > Sahitya, Chao,
> > >
> > > Could you please take a look at this patch and test intensively?
> > >
> > > Thanks,
> v3:
> - fix gc_lock
>
> From d10c09dfedc7a10cef7dd34493ddbd7c27889033 Mon Sep 17 00:00:00 2001
> From: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> Date: Tue, 31 Mar 2020 11:43:07 -0700
> Subject: [PATCH] f2fs: refactor resize_fs to avoid meta updates in progress
>
> Sahitya raised an issue:
> - prevent meta updates while checkpoint is in progress
>
> allocate_segment_for_resize() can cause metapage updates if
> it requires to change the current node/data segments for resizing.
> Stop these meta updates when there is a checkpoint already
> in progress to prevent inconsistent CP data.
>
> Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> ---
> fs/f2fs/checkpoint.c | 6 ++-
> fs/f2fs/f2fs.h | 2 +-
> fs/f2fs/file.c | 5 +-
> fs/f2fs/gc.c | 105 ++++++++++++++++++++----------------
> fs/f2fs/super.c | 1 -
> include/trace/events/f2fs.h | 4 +-
> 6 files changed, 67 insertions(+), 56 deletions(-)
>
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index 6be357c8e0020..dcb3a15574c99 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1554,7 +1554,8 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> return 0;
> f2fs_warn(sbi, "Start checkpoint disabled!");
> }
> - mutex_lock(&sbi->cp_mutex);
> + if (cpc->reason != CP_RESIZE)
> + mutex_lock(&sbi->cp_mutex);
>
> if (!is_sbi_flag_set(sbi, SBI_IS_DIRTY) &&
> ((cpc->reason & CP_FASTBOOT) || (cpc->reason & CP_SYNC) ||
> @@ -1623,7 +1624,8 @@ int f2fs_write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
> f2fs_update_time(sbi, CP_TIME);
> trace_f2fs_write_checkpoint(sbi->sb, cpc->reason, "finish checkpoint");
> out:
> - mutex_unlock(&sbi->cp_mutex);
> + if (cpc->reason != CP_RESIZE)
> + mutex_unlock(&sbi->cp_mutex);
> return err;
> }
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1241a397bf53c..e8e26ab723eba 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -194,6 +194,7 @@ enum {
> #define CP_DISCARD 0x00000010
> #define CP_TRIMMED 0x00000020
> #define CP_PAUSE 0x00000040
> +#define CP_RESIZE 0x00000080
>
> #define MAX_DISCARD_BLOCKS(sbi) BLKS_PER_SEC(sbi)
> #define DEF_MAX_DISCARD_REQUEST 8 /* issue 8 discards per round */
> @@ -1422,7 +1423,6 @@ struct f2fs_sb_info {
> unsigned int segs_per_sec; /* segments per section */
> unsigned int secs_per_zone; /* sections per zone */
> unsigned int total_sections; /* total section count */
> - struct mutex resize_mutex; /* for resize exclusion */
> unsigned int total_node_count; /* total node block count */
> unsigned int total_valid_node_count; /* valid node block count */
> loff_t max_file_blocks; /* max block index of file */
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index f06b029c00d8d..0514fab8d2eb8 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3313,7 +3313,6 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsigned long arg)
> {
> struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(filp));
> __u64 block_count;
> - int ret;
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
> @@ -3325,9 +3324,7 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsigned long arg)
> sizeof(block_count)))
> return -EFAULT;
>
> - ret = f2fs_resize_fs(sbi, block_count);
> -
> - return ret;
> + return f2fs_resize_fs(sbi, block_count);
> }
>
> static int f2fs_ioc_enable_verity(struct file *filp, unsigned long arg)
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index 26248c8936db0..3d003397252b8 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1399,12 +1399,29 @@ void f2fs_build_gc_manager(struct f2fs_sb_info *sbi)
> GET_SEGNO(sbi, FDEV(0).end_blk) + 1;
> }
>
> -static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
> - unsigned int end)
> +static int free_segment_range(struct f2fs_sb_info *sbi,
> + unsigned int secs, bool gc_only)
> {
> - int type;
> - unsigned int segno, next_inuse;
> + unsigned int segno, next_inuse, start, end;
> + struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
> + int gc_mode, gc_type;
> int err = 0;
> + int type;
> +
> + /* Force block allocation for GC */
> + MAIN_SECS(sbi) -= secs;
> + start = MAIN_SECS(sbi) * sbi->segs_per_sec;
> + end = MAIN_SEGS(sbi) - 1;
> +
> + mutex_lock(&DIRTY_I(sbi)->seglist_lock);
> + for (gc_mode = 0; gc_mode < MAX_GC_POLICY; gc_mode++)
> + if (SIT_I(sbi)->last_victim[gc_mode] >= start)
> + SIT_I(sbi)->last_victim[gc_mode] = 0;
> +
> + for (gc_type = BG_GC; gc_type <= FG_GC; gc_type++)
> + if (sbi->next_victim_seg[gc_type] >= start)
> + sbi->next_victim_seg[gc_type] = NULL_SEGNO;
> + mutex_unlock(&DIRTY_I(sbi)->seglist_lock);
>
> /* Move out cursegs from the target range */
> for (type = CURSEG_HOT_DATA; type < NR_CURSEG_TYPE; type++)
> @@ -1422,13 +1439,17 @@ static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
> up_write(&sbi->gc_lock);
> put_gc_inode(&gc_list);
>
> - if (get_valid_blocks(sbi, segno, true))
> - return -EAGAIN;
> + if (!gc_only && get_valid_blocks(sbi, segno, true)) {
> + err = -EAGAIN;
> + goto out;
> + }
> }
> + if (gc_only)
> + goto out;
>
> - err = f2fs_sync_fs(sbi->sb, 1);
> + err = f2fs_write_checkpoint(sbi, &cpc);
> if (err)
> - return err;
> + goto out;
>
> next_inuse = find_next_inuse(FREE_I(sbi), end + 1, start);
> if (next_inuse <= end) {
> @@ -1436,6 +1457,8 @@ static int free_segment_range(struct f2fs_sb_info *sbi, unsigned int start,
> next_inuse);
> f2fs_bug_on(sbi, 1);
> }
> +out:
> + MAIN_SECS(sbi) -= secs;
> return err;
> }
>
> @@ -1481,6 +1504,7 @@ static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)
>
> SM_I(sbi)->segment_count = (int)SM_I(sbi)->segment_count + segs;
> MAIN_SEGS(sbi) = (int)MAIN_SEGS(sbi) + segs;
> + MAIN_SECS(sbi) += secs;
> FREE_I(sbi)->free_sections = (int)FREE_I(sbi)->free_sections + secs;
> FREE_I(sbi)->free_segments = (int)FREE_I(sbi)->free_segments + segs;
> F2FS_CKPT(sbi)->user_block_count = cpu_to_le64(user_block_count + blks);
> @@ -1502,8 +1526,8 @@ static void update_fs_metadata(struct f2fs_sb_info *sbi, int secs)
> int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> {
> __u64 old_block_count, shrunk_blocks;
> + struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
> unsigned int secs;
> - int gc_mode, gc_type;
> int err = 0;
> __u32 rem;
>
> @@ -1538,10 +1562,22 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> return -EINVAL;
> }
>
> - freeze_bdev(sbi->sb->s_bdev);
> -
> shrunk_blocks = old_block_count - block_count;
> secs = div_u64(shrunk_blocks, BLKS_PER_SEC(sbi));
> +
> + /* protect MAIN_SEC in free_segment_range */
> + f2fs_lock_op(sbi);
> + err = free_segment_range(sbi, secs, true);
> + f2fs_unlock_op(sbi);
> + if (err)
> + return err;
> +
> + set_sbi_flag(sbi, SBI_IS_RESIZEFS);
> +
> + freeze_super(sbi->sb);
> + down_write(&sbi->gc_lock);

free_segment_range() tries to acquire the gc_lock before do_garbage_collect().
It can deadlock.

Thanks,

> + mutex_lock(&sbi->cp_mutex);
> +
> spin_lock(&sbi->stat_lock);
> if (shrunk_blocks + valid_user_blocks(sbi) +
> sbi->current_reserved_blocks + sbi->unusable_block_count +
> @@ -1550,69 +1586,44 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count)
> else
> sbi->user_block_count -= shrunk_blocks;
> spin_unlock(&sbi->stat_lock);
> - if (err) {
> - thaw_bdev(sbi->sb->s_bdev, sbi->sb);
> - return err;
> - }
> -
> - mutex_lock(&sbi->resize_mutex);
> - set_sbi_flag(sbi, SBI_IS_RESIZEFS);
> -
> - mutex_lock(&DIRTY_I(sbi)->seglist_lock);
> -
> - MAIN_SECS(sbi) -= secs;
> -
> - for (gc_mode = 0; gc_mode < MAX_GC_POLICY; gc_mode++)
> - if (SIT_I(sbi)->last_victim[gc_mode] >=
> - MAIN_SECS(sbi) * sbi->segs_per_sec)
> - SIT_I(sbi)->last_victim[gc_mode] = 0;
> -
> - for (gc_type = BG_GC; gc_type <= FG_GC; gc_type++)
> - if (sbi->next_victim_seg[gc_type] >=
> - MAIN_SECS(sbi) * sbi->segs_per_sec)
> - sbi->next_victim_seg[gc_type] = NULL_SEGNO;
> -
> - mutex_unlock(&DIRTY_I(sbi)->seglist_lock);
> + if (err)
> + goto out_err;
>
> - err = free_segment_range(sbi, MAIN_SECS(sbi) * sbi->segs_per_sec,
> - MAIN_SEGS(sbi) - 1);
> + err = free_segment_range(sbi, secs, false);
> if (err)
> - goto out;
> + goto recover_out;
>
> update_sb_metadata(sbi, -secs);
>
> err = f2fs_commit_super(sbi, false);
> if (err) {
> update_sb_metadata(sbi, secs);
> - goto out;
> + goto recover_out;
> }
>
> - mutex_lock(&sbi->cp_mutex);
> update_fs_metadata(sbi, -secs);
> clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
> set_sbi_flag(sbi, SBI_IS_DIRTY);
> - mutex_unlock(&sbi->cp_mutex);
>
> - err = f2fs_sync_fs(sbi->sb, 1);
> + err = f2fs_write_checkpoint(sbi, &cpc);
> if (err) {
> - mutex_lock(&sbi->cp_mutex);
> update_fs_metadata(sbi, secs);
> - mutex_unlock(&sbi->cp_mutex);
> update_sb_metadata(sbi, secs);
> f2fs_commit_super(sbi, false);
> }
> -out:
> +recover_out:
> if (err) {
> set_sbi_flag(sbi, SBI_NEED_FSCK);
> f2fs_err(sbi, "resize_fs failed, should run fsck to repair!");
>
> - MAIN_SECS(sbi) += secs;
> spin_lock(&sbi->stat_lock);
> sbi->user_block_count += shrunk_blocks;
> spin_unlock(&sbi->stat_lock);
> }
> +out_err:
> + mutex_unlock(&sbi->cp_mutex);
> + up_write(&sbi->gc_lock);
> + thaw_super(sbi->sb);
> clear_sbi_flag(sbi, SBI_IS_RESIZEFS);
> - mutex_unlock(&sbi->resize_mutex);
> - thaw_bdev(sbi->sb->s_bdev, sbi->sb);
> return err;
> }
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index f2dfc21c6abb0..18b4a43a13438 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3413,7 +3413,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> init_rwsem(&sbi->gc_lock);
> mutex_init(&sbi->writepages);
> mutex_init(&sbi->cp_mutex);
> - mutex_init(&sbi->resize_mutex);
> init_rwsem(&sbi->node_write);
> init_rwsem(&sbi->node_change);
>
> diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> index e78c8696e2adc..e1ad392aae05a 100644
> --- a/include/trace/events/f2fs.h
> +++ b/include/trace/events/f2fs.h
> @@ -50,6 +50,7 @@ TRACE_DEFINE_ENUM(CP_RECOVERY);
> TRACE_DEFINE_ENUM(CP_DISCARD);
> TRACE_DEFINE_ENUM(CP_TRIMMED);
> TRACE_DEFINE_ENUM(CP_PAUSE);
> +TRACE_DEFINE_ENUM(CP_RESIZE);
>
> #define show_block_type(type) \
> __print_symbolic(type, \
> @@ -126,7 +127,8 @@ TRACE_DEFINE_ENUM(CP_PAUSE);
> { CP_RECOVERY, "Recovery" }, \
> { CP_DISCARD, "Discard" }, \
> { CP_PAUSE, "Pause" }, \
> - { CP_TRIMMED, "Trimmed" })
> + { CP_TRIMMED, "Trimmed" }, \
> + { CP_RESIZE, "Resize" })
>
> #define show_fsync_cpreason(type) \
> __print_symbolic(type, \
> --
> 2.26.0.110.g2183baf09c-goog
>

--
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